Grow Your Own Shamrock Indoors

It is said that on St. Patrick’s Day, March 17, everybody is Irish. Okay, but are you an Irish gardener? If so, why not grow an Irish shamrock in your home?

A Plant of Legend

The shamrock is a legendary plant with three leaflets. Saint Patrick is said to have used it to teach the Holy Trinity to the pagan Irish back in the 7^th century, converting them to Christianity. The problem is that nobody really knows which leaf he used: was it a clover, an alfalfa or an oxalis? The Irish name shamrock is of no help. It means, quite literally, “small three-leaved plant”, which could mean just about anything. I figure this gives the indoor gardener a certain freedom of choice, but since neither clover (Trifolium) nor alfalfa (Medicago) make good houseplants – and since both are solidly frozen outdoors in most regions on Saint Patrick’s Day – I suggest using the oxalis as a living symbol of your Irish heritage.

An Indoor Shamrock

The false shamrock, also called purple shamrock or love plant (Oxalis triangularis, formerly O. regnellii) is probably the best species to use as a houseplant. It is adapted to subtropical conditions and thus easier to grow in the average heated home than more temperate oxalis species. Of course, since it hails from South America, it is certainly not the true Irish shamrock… but if you don’t tell anyone, I won’t either.

The distinguishing feature of this plant is that each of the three leaflets that make up its leaf is almost triangular. They are carried on long petioles, upright at first, but eventually arching or even drooping under typical indoor conditions, forming a dome as wide as it is tall. The leaflets have the curious habit of closing at night, folding one against the other.

The leaves of the false shamrock were originally plain green, but there are now many cultivars with purple foliage or with a silver or metallic pink mark on the leaflets. Similarly, the five-petaled flowers, which were white in the original species, are pink in the case of many cultivars.

False shamrock grows throughout the year indoors and is almost never without flowers. Out of sight under the soil are scaly rhizomes in which it stores energy for future use. So if you ever stop watering your oxalis, it won’t die but will simply go dormant and lose its leaves. It will then grow back from its underground rhizomes when you start to water it again. That’s because plant evolved to cope with occasional droughts in its natural environment.

This makes it the perfect plant for Snowbirds, as they can leave their oxalis totally on its own for six months without having to worry about having someone come in to water it, then it will grow back quickly when they get home and start to water it again. The rhizomes are also used for multiplication. Just dig up one or two, pot them up and you’ll quickly have a pot of true false Irish shamrock to share with friends and neighbors.

How to Grow False Shamrock

This is a very easy houseplant to care for.

Average home temperatures suit it perfectly (at less than 50°F/10°C or more than 90°F/32°C, however, it may go dormant) and it adapts to most light situations, from dim to bright. However, it prefers bright light during the winter. It also tolerates dry air, although it does better in a humid atmosphere. The only truly essential maintenance is watering: to keep growing, water it regularly, whenever the soil feels dry to the touch. You can add a diluted dose of the fertilizer of your choice between March and October… but even if you do never fertilize your oxalis, it will still grow very well.

In addition, false shamrock rarely suffers from insects or diseases. If you ever detect a problem, you can quickly solve it: chop the leaves to the ground to eliminate the pest and the plant will grow back quickly. After two weeks, your plant will be healthy again, new leaves will be growing and it will soon be in bloom!

So much for the good news. On the negative side, false shamrock is a messy plant, requiring frequent cleaning. The leaves and flowers are short-lived and if you don’t remove the faded ones every three or four days, they build up and diminish the plant’s attractiveness.

Surprising Facts

Curiously, false shamrock is grown as a vegetable in many South American countries. People consume the leaves and flowers, but especially the rhizomes, serving them either as a side dish or a condiment. All have a delightfully tangy taste, like sorrel or rhubarb. Don’t overdo it though, as all its parts contain oxalic acid which is toxic if consumed in large quantities. In South America, it is generally held that you should not eat oxalis more than three or four times a week.

If you have pets (dogs, cats, etc.) be forewarned that they don’t know that they should be consuming this plant in moderation and could become sick if they eat too much. Most pets don’t like the taste of false shamrock and will stop chewing after the first nibble. However, if your little friend is given to munching plant parts, you’d do best to keep your oxalis out of its reach.

You can also use this oxalis outdoors during the summer, in pots or planted in the garden, in sun or shade. The easiest thing to do is to cut the leaves to the ground before you plant it out. That way you won’t have to worry about slowly acclimating the plant to outdoor conditions like you would with most plants you’re transitioning to outdoor growing; the new leaves that grow in will automatically adapt to outdoor sun.

This oxalis is hardy from USDA zone 7 to 10. It therefore won’t be hardy in northern climates and will have to be brought back indoors in the fall. It warmer climes it can remain outdoors all year. Unlike many oxalis species, false shamrock is not invasive and will remain in its place unless you disturb the rhizomes. Rototilling, notably, could spread them far and wide.

Beannachtai na Feile Padraig! (“Happy St. Patrick’s Day!” in Gaelic.)